A Pesticide Information Project of Cooperative Extension Offices of
Cornell University, Michigan State University, Oregon State University, and
University of California at Davis. Major support and funding was provided
by the USDA/Extension Service/National Agricultural Pesticide Impact
Assessment Program.

PesticideInformationProfile

Carbofuran

Publication Date: 9/93

TRADE OR OTHER NAMES

REGULATORY STATUS

Following a Special Review which began in 1985, the EPA initiated a
ban on all granular formulations of carbofuran, with five minor-use
exceptions, to become effective on September 1, 1994. Phase-out began
on September 1, 1991 with a ban on the use of granular carbofuran in
certain ecologically sensitive areas. Before 1991, 80 percent of the
total usage of carbofuran was in granular formulations. The ban has
been established to protect birds and is not related to human health
concerns. Bird kills have occurred when birds ingested carbofuran
granules, which resemble grain seeds in size and shape, or when
predatory or scavenging birds have ingested small birds or mammals which
had eaten carbofuran pellets. There is no ban on liquid formulations of
carbofuran (27, 28).

Liquid formulations of carbofuran are classified as Restricted Use
Pesticides (RUP) because of their acute oral and inhalation toxicity to
humans. Granular formulations are also classified as RUP's, but for a
different reason, their toxicity to birds. Liquid formulations bear the
signal word "Danger." Granular formulations bear the signal word
"Caution" (25).

INTRODUCTION

Carbofuran is a broad spectrum carbamate pesticide that kills
insects, mites and nematodes on contact or after ingestion. It is used
against soil and foliar pests of field, fruit, vegetable and forest
crops. Carbofuran is available in liquid and granular formulations (5,
25, 27, 28).

TOXICOLOGICAL EFFECTS

ACUTE TOXICITY

Carbofuran is highly toxic by inhalation and ingestion and
moderately toxic by dermal absorption (6, 30). Risks from exposure to
carbofuran are especially high for persons with asthma, diabetes,
cardiovascular disease, mechanical obstruction of the gastrointestinal
or urogenital tracts, or those in vagotonic states (30).

Carbofuran may cause contact burns to the skin or eyes (13). Eye
protection should be worn when handling carbofuran. A respirator should
be worn by applicators of carbofuran (1). Fires, and the run off from
fire control, may produce irritating or poisonous gases (13). Closed
spaces (storage, etc.) should be aired before entering (13).

As with other carbamate compounds, carbofuran's cholinesterase-
inhibiting effect is short-term and reversible (7). Symptoms of
carbofuran poisoning include: nausea, vomiting, abdominal cramps,
sweating, diarrhea, excessive salivation, weakness, imbalance, blurring
of vision, breathing difficulty, increased blood pressure or
'hypertension,' and lack of control of urine or feces release, referred
to as 'incontinence.' Death may result from respiratory system failure
associated with carbofuran exposure (4). Complete recovery from an
acute poisoning by carbofuran, with no long term health effects, is
possible if exposure ceases and the victim has time to reform their
normal level of cholinesterase and to recover from symptoms (7, 24).
(For more information on cholinesterase, please refer to the Toxicology
Information Brief on Cholinesterase-Inhibition).

Carbamates generally are excreted rapidly and do not accumulate in
mammalian tissue. If exposure does not continue, cholinesterase
inhibition reverses rapidly. In non-fatal cases, the illness generally
lasts less than 24 hours (30).

The amount of a chemical that is lethal to one-half (50%) of
experimental animals fed the material is referred to as its acute oral
lethal dose fifty, or LD50. The oral LD50 for rats is 5 mg/kg, for mice
is 2 mg/kg, and for dogs is 19 mg/kg. The dermal LD50 for rabbits is
885 mg/kg (30).

The lethal concentration fifty, or LC50, is that concentration of a
chemical in air or water that kills half of the experimental animals
exposed to it for a set time period. The 4-hour LC50 for inhalation of
carbofuran in guinea pigs is 43 mg/m3. The LC50 for rats is 85 mg/L and
52 mg/L for dogs (30).

CHRONIC TOXICITY

Prolonged or repeated exposure to carbofuran may cause the same
symptoms as an acute exposure (30). The EPA has established a Lifetime
Health Advisory (LHA) level of 40 ppb of carbofuran in drinking water.
This means that a person may drink water containing carbofuran at or
below this level daily over the course of their lifetime with no health
effects. Consuming carbofuran at high levels well above the LHA level
over a long period of time has caused damage to the testes and uterus of
test animals. It has also caused cholinesterase inhibition in both
humans and test animals (29).

Reproductive Effects

Teratogenic Effects

The lowest amount of carbofuran that proved teratogenic to mice in
the mother's diet (TDlo) was 210 ug/kg (fed throughout pregnancy) (NIOSH
RTECS Online File 304/8311).

Mutagenic Effects

No mutagenic effects have been reported in animals or bacteria
(using the Ames Assay: J. Toxicol. Environ. Health 7(3-4):519-
531.1981). Genetic changes have been shown in algae (Microbios. Lett.
12(46):79.1979).

Carcinogenic Effects

Sufficient data are available from animal studies to indicate that
carbofuran does not pose a risk of cancer to humans (29). However, N-
nitrosocarbamates are potent mutagens and carcinogens. They can be made
under the acidic conditions of the stomach of some animals. Humans are
possible candidates (J. Toxicol. Environ. Health 14(2-3):279- 290.1984).

Fate in Humans and Animals

Carbofuran is poorly absorbed through the skin (19). It is
metabolized (broken-down) in the liver and eventually excreted in the
urine. The half-life is from 6-12 hours. About 3% of the mother's
intake will be excreted in the milk (Menzie. Metab. Pesticides. 1974).

Carbamates generally are excreted rapidly and do not accumulate in
mammalian tissue. If exposure does not continue, cholinesterase
inhibition reverses rapidly. In non-fatal cases, the illness generally
lasts less than 24 hours (30).

ECOLOGICAL EFFECTS

Effects on Birds

Carbofuran is highly toxic to birds. One granule is sufficient to
kill a small bird. Bird kills have occurred when birds ingested
carbofuran granules, which resemble grain seeds in size and shape, or
when predatory or scavenging birds have ingested small birds or mammals
which had eaten carbofuran pellets (28).

Carbofuran is very toxic to pheasants, chickens, fulvous tree ducks
and Japanese quail (4). Red shouldered hawks have been poisoned after
eating prey from carbofuran treated fields (J. Wildlife Manage.
47(4):1129. 1983). Levels of carbofuran occurring in Kansas fields have
been high enough to cause a reduction in the weight, food intake and
ability to move of adult male bobwhites (Arch. Environ. Contam. Toxicol.
11(5):611-615.1982).

ENVIRONMENTAL FATE

Breakdown of Chemical in Soil and Groundwater

Carbofuran is soluble in water and has a moderately lengthy soil
half-life (3-60 days). It is therefore expected to have a high
potential for groundwater contamination (31, Curr. Sci.
53(17):925.1984.). Carbofuran was mobile to very mobile in sandy , silt
loam, silty clay and silty clay loam soils; moderately mobile in silty
clay and silty clay loam soils; and only slightly mobile in muck soils.
Carbofuran has been detected at very low (1 to 5 ppb) in water table
aquifers beneath sandy soils in New York and Wisconsin (29).

In soil, carbofuran is degraded by chemical hydrolysis and
microbial processes. Hydrolysis occurs more rapidly in alkaline soils
(29). Soil microorganisms are better at breaking down large amounts of
carbofuran if the soil is pretreated with a small amount of carbofuran
(J. Environ. Sci. Health Part B, B-19 (1):111.1984). Carbofuran breaks
down in sunlight (Menzie. Metab. Pesticides. 1969.).

Breakdown of Chemical in Water

In water, carbofuran is subject to degradation by chemical
hydrolysis under alkaline conditions. Photodegradation and aquatic
microbes may also contribute to degradation. The hydrolysis half-lives
of carbofuran in water at 25 degree C are 690, 8.2, and 1.0 weeks at
pH's of 6.0., 7.0, and 8.0 respectively. Carbofuran does not volatilize
from water nor does it adsorb to sediment or suspended particles. It
does not bioaccumulate in aquatic systems (29).

Fire control run-off or dilution water may cause pollution of lakes
and/or streams (13).

Breakdown of Chemical in Vegetation

The half-life of carbofuran on crops, when applied to the roots, is
about 4 days and longer than 4 days if applied to the leaves (Menzie.
Metab. Pesticides. 1974).